1. Field of the Invention
The present invention relates to a spark plug having a low noise level, and more particularly relates to a spark plug incorporating a winding type inductor and having a high noise-attenuation effect over a wide frequency range.
2. Description of the Prior Art
Recently, noise and electric wave disturbance have been legally restricted in Canada and other countries and are going to be legally restricted in many countries. In order to satisfy these demands, a shield type plug cap incorporating a winding type inductor is mainly used as a spark plug for internal combustion engines, such as a snow mobile, outboard engine and the like.
However, the shield-type plug cap has such drawbacks that voltage drop due to a large electrostatic capacity occurs, and particularly leakage of electric current occurs under a high-moisture environment, such as rainfall.